GXSC DAC Replaces AD9747 in RF Instruments

RF test instruments are characterized by wide bandwidth, high precision, low spurious emissions, and low noise. Their main modules include a digital waveform generator, a high-speed DAC, an upconverter, and an amplifier-filter unit. After the instrument generates various waveforms, the high-speed DAC performs the conversion, and the analog signal is fed into a modulator for upconversion, generating RF signals in the corresponding frequency bands for fault detection and performance verification of wireless terminals and RF modules.

Among these components, the waveform reproduction accuracy, signal purity, and response bandwidth of the instrument’s high-speed DAC determine the test performance of the RF instrument. This solution utilizes the GXSC dual-channel 16-bit 250 MSPS high-performance digital-to-analog converter (DAC). Its high-speed, high-precision characteristics eliminate issues such as bandwidth limitations and waveform clipping distortion, enabling the complete reproduction of high-frequency, broadband, and transient RF test waveforms.

The GXSC DAC includes specific features for direct conversion in transmission applications, such as gain and offset compensation, and can interface seamlessly with analog quadrature modulators. A proprietary dynamic output architecture enables analog output synthesis even beyond the Nyquist frequency by shifting energy from the fundamental frequency to the image frequency. A Serial Peripheral Interface (SPI) port provides full programmability. Additionally, for applications without a controller, several pin-programmable features are available.

GXSC DAC Features:

 High dynamic range, dual DAC

Low noise and intermodulation distortion

Single-carrier W-CDMA ACLR = 80 dBc (61.55 MHz)

Innovative switched output stage, allowing output frequencies exceeding the Nyquist frequency

Includes dual-port LVCMOS inputs or selectable cross-access single-port operation

Differential analog current output programmable from 8.6 mA to 31.7 mA

 Auxiliary 10-bit current DAC with sink/source capability for use in external zero-offset compensation circuits

 Built-in 1.2V precision reference voltage source

 Operating supply: 1.8V–3.3V

 Power consumption: 315mW

 Operating temperature: –55°C to +125°C

QFN72 package, replacement for AD9747